MX2007013956A - Low iv pet based copolymer preform with enhanced mechanical properties and cycle time, container made therewith and methods. - Google Patents

Abstract

A preform having a low IV and comprising a PET Copolymer comprising a diol component having repeat units from ethylene glycol and diethylene glycol and a diacid component having repeat units from terephthalic acid and naphthalenedicarboxylic acid. The total amount of diethylene glycol and naphthalenedicarboxylic acid is present in the poly(ethylene terephthalate) copolymer in an amount from about 0.1 mole percent to less than 2.8 mole percent. The preform is useful in making containers and corresponding methods are disclosed.

Description

COPOLYMER PREFORMA BASED ON VI LOW PET WITH MECHANICAL PROPERTIES AND IMPROVED CYCLE TIME, RECIPIENT MADE WITH THE SAME AND METHODS Field of the Invention This invention relates to preforms and their containers made of resin compositions based on low intrinsic viscosity and low stretch ratio of polyethylene terephthalate.

BACKGROUND OF THE INVENTION Polyethylene terephthalate and its copolymers, which are commonly referred to in the industry as "PET", have been widely used to manufacture containers for juice, water, carbonated soft drinks ("CSD") and the like because of their light weight and excellent combination of mechanical and gas barrier properties, however, a higher molecular weight PET should be used due to a phenomenon called environmental stress cracking. High molecular weight PET has a high intrinsic viscosity (VI). Traditionally, a minimum IV of 080 dL / g is desired to create a CSD container, preferred VIs being reported to be 0.82 dL / g or higher. The upper VI or PET of higher molecular weight has a VI above 0.80 dL / g and fewer chain ends and is thought to have less interaction with etching agents, and therefore has less stress cracking. In addition, it is thought that the PET of the upper VI is entangled more chains that can dissipate more tension than PET of lower IV. However, higher VI PET requires longer solid state polymerization time (SSP) and higher injection molar temperature due to the higher melt viscosity. The upper injection molding temperature means more degradation of PET during injection molding and higher energy consumption. The upper VI PET is also more expensive to form than the lower VI PET. However, the general trend in recent years is the use of PET that has VI of approximately 0.84 dL / g or higher to avoid discomfort from the environmental stress cracking problem, although higher VI PET costs more to produce and more expenses to convert it from resin to container. Lower VI PET, although it costs less to produce or convert, does not have sufficient mechanical strength. This is shown not only by the lower stress cracking strength of the VI PET, but also in the natural stretch ratio of the PET.

It is well known to those skilled in the art that the natural stretch ratio is an inherent property of PET. The natural stretch ratio of PET depends on the PET composition, the VI of the PET, the stretching temperature and the stretching regime. Under the same stretching temperature and regime, the natural stretch ratio of PET decreases with an increase in VI or molecular weight. It is thought that the decrease is caused by the entanglement of higher molecular weight PET chains. In applications of the container, the container is made of an injection molding process. A preform is first molded by injection and then blow molded into containers either in a one-step or two-step process. The natural stretch ratio determines the preform design. When designing a preform, it is important that the stretch ratio of the corresponding bottle preform is more than the natural stretch ratio of the polymer so that the polymer can reach and pass the stress hardening point. Only after the PET stretches pass the stress hardness point will it start forming the stable orientation and stress-induced crystallinity. If the preform is designed in such a way that the polymer does not reach the point of hardness during the blow molding or reaches the hardening point, the resulting orientation and crystallinity in the bottle will be substantially lower and the distribution of the material in the bottle will not it will be more uniform. These properties, in turn, not only impact the mechanical properties of the bottle but the lateral wall stiffness and thermal expansion under pressure, which affect the gas permeation through the side wall of the containers and the shelf life of the stored product in the containers. Therefore, it is very important that the preform be designed in accordance with the stretch ratio of the polymer. The stretch ratio as used herein is the nomenclature that will be well known in the art and is defined as follows: Overall stretch ratio = (maximum internal container diameter / internal preform diameter)] x [container height below finish) / (preform height below finish)]. Since the upper VI PET has a lower natural stretch ratio, a lower stretch ratio preform can be used for higher VI PET. It is also well known to those skilled in the art that the lower stretch ratio preform means a larger or larger diameter preform with a thinner side wall under the same preform weight. The thinner side wall means faster cooling during injection molding (the cooling time is proportional to the square of the sidewall thickness) and shorter cycle time. For a common bottle grade low VI PET that is modified with IpA or CHDM, the preform must have a higher stretch ratio to be molded into containers such as bottles. The upper stretch ratio preform means thicker sidewalls and larger cooling time which results in reduced productivity. If a preform is designated for upper PET VI and low VI is used for molding said preforms, the material will not stretch properly when it is blown into bottles and will suffer from the crystallinity and orientation of the side wall. This will cause an increase in the sweep for CSD vessels and a decrease in the stiffness of the side wall of the bottles. Therefore, there is a need in the art for a lower VI PET preform having a conventional configuration normally used for upper VI PET, but it is also useful for forming containers having adequate mechanical properties and residence to stress cracking.

SUMMARY OF THE INVENTION This invention addresses the above needs to provide a low VI PET copolymer preform having a talc stretch ratio or a traditional high VI PET preform configuration that can be used to create containers with the preform despite VI lower. Typically, a lower VI PET preform could mean that the preform could have a higher stretch ratio to form a container with desirable mechanical properties. The preform of the present invention, however, defines the convention, and produces a container with suitable mechanical properties although it has lower VI and a lower stretch ratio. Due to this unique combination of characteristics, the preform of this invention can be used to create containers at a shorter cycle time than a higher VI PET preform. More particularly, the preform of this invention comprises a polyethylene terephthalate copolymer comprising a diol component having repeating units of ethylene glycol and diethylene glycol and a diacid component having repeated units of terephthalic acid and naphthalenedicarboxylic acid wherein, based on 100 mole percent of the diol component and 100 mole percent of the diacid component, respectively, the total amount of diethylene glycol and naphthalenedicarboxylic acid present in the PET copolymer is in an amount of about 0.1 mole percent less than about 2.8 mole percent . In addition, the preform has an intrinsic viscosity better than 0.77 dL / g. This means that the molar percentage of diethylene glycol is based on the 100 mole percent diol component and the mole percentage of naphthalenedicarboxylic acid is based on the 100 mole percent diacid component. This definition can be applied to molar percentages through this specification. This invention also encompasses a container made with the preform described above and method for creating the preform and container. In addition, this invention encompasses a method for reducing the cycle time to create a container comprising the steps of: (1) providing a PET copolymer melt comprising a diol component having repeating units of ethylene glycol and diethylene glycol and a component of diacid having repeated units of terephthalic acid and naphthalenedicarboxylic acid, wherein, based on 100 mole percent of the diol component and 100 mole percent of the diacid component, respectively, the total amount of diethylene glycol and naphthalenedicarboxylic acid present in the copolymer of PET is an amount from about 0.1 mole percent to less than about 2.8 mole percent, (2) then injecting the PET copolymer into a mold, (3) then cooling the mold and the contained polymer, (4) then releasing of the mold a preform that has an intrinsic viscosity less than 0.77 dL / g. (5) then reheating the preform, and (6) then blow molding the preform into a container; wherein the cycle time to create the container is reduced compared to a second cycle time to create a second container with a preform comprising a PET Copolymer and having an intrinsic viscosity of at least 0.77 dL / g. Other objects, aspects and advantages of this invention will be apparent from the following detailed description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional elevation view of an injection molded preform having a conventional configuration and made with the PET copolymer according to a preferred embodiment of this invention. Fig. 2 is a sectional elevation view of a blow molded container made of the preform of Fig. 1 according to a preferred embodiment of this invention.

DETAILED DESCRIPTION OF MODALITIES This invention encompasses a low VI PET Copolymer preform having a low stretch ratio as well as a container made with the preform described above and methods for creating the preform and container. further, this invention encompasses a method for reducing the cycle time to create a container. According to one embodiment, a PET copolymer is created in an injection molded preform which is then blow molded into a container. The preform of this invention comprises a polyethylene terephthalate copolymer comprising a diol component having repeating units of ethylene glycol and diethylene glycol and a diacid component having repeating units of terephthalic acid and naphthalenedicarboxylic acid wherein, based on 100 mole percent of the diol component and 100 mole percent of the diacid component, respectively, the total amount of diethylene glycol and naphthalenedicarboxylic acid present in the PET copolymer is in an amount of about 0.1 mole percent less than about 2.8 mole percent. In addition, the preform has an intrinsic viscosity better than 0.77 dL / g. This means that the molar percentage of diethylene glycol is based on the 100 mole percent diol component and the mole percentage of naphthalenedicarboxylic acid is based on the 100 mole percent diacid component. This definition can be applied to molar percentages through this specification. The amount of each of diethylene glycol and naphthalenedicarboxylic acid in the PET Copolymer can vary some degree within the total amount of both. In preferred embodiments, the total amount of diethylene glycol and naphthalenedicarboxylic acid is present in the polyethylene terephthalate copolymer in an amount of about 1.1 mole percent to about 2.8 mole percent, and more preferably, in an amount of about 1.2 percent molar to around 2.3 molar percent. The diethylene glycol present in the PET copolymer preferably is in the amount of 1.3 to about 2.5 mole percent and more preferably 1.5 to 2.2 mole percent. The naphthalenedicarboxylic acid present in the PET copolymer is preferably in the amount of 0.2 to 1 mole percent, preferably 0.2 to 0.75 mole% and more preferably 0.25 to 0.75 mole percent. The PET copolymer preform preferably has an intrinsic viscosity (VI), measured in accordance with ASTM D4603-96 less than 0.77 dL / g, preferably from about 0.6 to less than about 0.77 dL / g, more preferably from about 0.70 to less. of about 0.76 dL / g, and even more preferably from about 0.70 to about 0.74 dL / g. Conveniently, the preform of this invention comprises a reaction grade PET copolymer resin, which means that the PET resin is a direct product of a chemical reaction between comonomers and a non-polymeric mixture. The preferred terephthalate-free acid diacid component is 2,6-naphthalene dicarboxylic acid (NDC). The DEG levels in the PET copolymers of the present invention range from about 0.1 to about 2.0 mole percent, which is below the normal residual levels of DEG present in conventional PET manufacturing (hereinafter "PET"). Conventional "). Conventional PET typically contains about 24. about 2.9 mole percent of DEG, which is equivalent to percent values by weight more commonly called from about 1.3 to about 1.6. Experts in the field of PET manufacturing generally with respect to DEG as a harmless byproduct of polymer manufacturing; consequently, efforts have been directed towards the reduction of SDR levels in PET that is intended to be used in containers. Therefore, modifications of the container PET production process should occur to achieve the lower DEG levels in the PET copolymer used to create the preform of the present invention. Any suitable method for reducing the polyester DEG content can be employed. Suitable methods include reducing the molar ratio of diacid or diester relative to ethylene glycol in the esterification or transesterification reaction, addition of DEG suppressive additives, including tetra-alkylammonium salts and the like; and reducing the DEG content of the ethylene glycol that is recycled back to the esterification or transesterification reaction. In the embodiments of this invention, in spite of low VI and conventional configuration, the preforms have a stretch ratio in the scale of about 8 to about 13 when used to create containers, and more conveniently about 8 to about 12. The stretch ratio as used herein refers to the nomenclature that is well known in the art and is defined as follows: Overall stretch ratio = (maximum internal container diameter / internal preform diameter)] x [container height below finish) / (preform height below finish)]. The natural stretch ratio is an inherent property of a polymer. The measurement of the free blowing volume of a polymer relative to a preform used in the present Examples provides a method for measuring the natural stretch ratio of a polymer. The natural stretch ratio of a polymer influences the design of the preform by determining the stretch ratio limitations of a preform used in the blow molding process to create a container. A polyhedron with a lower natural stretch ratio allows a preform with a lower stretch ratio to be designated. With an understanding of the natural stretching ratio of a polymer, the dimensions of the preform such as height, inner diameter and wall thickness can be selected such that the preform can be blow molded into a container having certain selected physical properties such as weight, height, maximum diameter, thermal stability, and lateral wall stiffness. In another embodiment of the present invention, a method for eliciting the cycle time to create a container comprises the steps of: (1) providing a PET copolymer fusion comprising a diol component having repeated units of ethylene glycol and diethylene glycol and a diacid component having repeated units of terephthalic acid and naphthalenedicarboxylic acid, wherein, based on 100 mole percent of the diol component and 100 mole percent of the diacid component, respectively, the total amount of diethylene glycol and naphthalenedicarboxylic acid present in the PET copolymer is an amount from about 0.1 mole percent to less than about 2.8 mole percent, (2) then injecting the PET copolymer into a mold, (3) then cooling the mold and the contained polymer, (4) ) then releasing from the mold a preform having an intrinsic viscosity less than 0.77 dL / g. (5) then reheating the preform, and (6) then blow molding the preform into a container; wherein the cycle time to create the container is reduced compared to a second cycle time to create a second container with a preform comprising a PET copolymer and having an intrinsic viscosity of at least 0.77 dL / g.

In yet another embodiment of the method, a method for creating a preform for use in creating containers comprises injection molding a PET copolymer, comprising a diol component having repeating units of ethylene glycol and a diethylene glycol and a diacid component having repeating units of ethylene glycol and a diethylene glycol and a diacid component having repeated units of terephthalic acid and naphthalenedicarboxylic acid. The total amount of diethylene glycol and naphthalenedicarboxylic acid present in the PET copolymer is in an amount of about 0.1 mole percent to about 2.8 mole percent and the preform has an intrinsic viscosity of less than 0.77 dL / g. In yet another embodiment, a method for creating a container comprises blow molding an injection molded preform having an open end mouth forming portion, an intermediate body forming portion and a closed base forming portion, and comprises a PET copolymer. The PET copolymer comprises a diol component having repeating units of ethylene glycol and diethylene glycol and a diacid component having repeated units of terephthalic acid and naphthalenedicarboxylic acid. The total amount of diethylene glycol and naphthalenedicarboxylic acid present in the PET copolymer is in an amount of about 0.1 mole percent to about 2.8 mole percent and the preform has an intrinsic viscosity of less than 0.77 dL / g. A co-pending patent application entitled "Preform For The Natural Stretch Ratio PET Copolymer, Container Made Therewith and Methods "and filed on May 11, 2005, the description of which is hereby expressly incorporated by reference, discloses a preform that has a reduced stretch ratio with some ring relationship and axial ratio limitations made of an LNSR polymer having a lower natural stretch ratio on preforms made of PET reed available in the prior art This reference also discloses a stretch blown pore container having excellent mechanical properties, in particular a beverage container, made of this preform design Also, this reference discloses a clear container or container blow molded by stretching, substantially clear, free of mist or substantially free of haze In addition, the LNSR polymer is described separately and is claimed in the Application U.S. Patent No. 10 / 967,803 filed in the Patent and Trademark Office of E.U.A. on October 18, 2004, which is a continuation of the U.S. Patent Application. Series No. 10 / 696,858 filed in the Patent and Trademark Office of E.U.A. on October 30, 2003, which claims priority under 35 U.S.C. §119 to the United States Provisional Patent Application Series No. 60 / 423,221 filed on November 1, 2002, the descriptions of which are incorporated herein in their entirety by this reference. In particular, the embodiments of this invention are suitable for creating containers for packaging applications in the soft non-carbonated beverage industry and the food industry. The PET copolymer preforms are made by forming the polyester compositions described above in the preform by conventional methods such as melt formation. Suitable melt forming processes including, but not limited to, injection molding, extrusion, thermal forming and compression molding. The containers are made of preforms in a single flange, two stages and double manufacturing system of blow molding. Such methods are well known to those skilled in the art and examples of suitable preforms and suitable vessel structures are described in the U.S. Patent. No. 5,888,598, the disclosure of which is hereby incorporated by reference in its entirety. Another preform and blow molded container structures by stretching known to one skilled in the art can also be prepared in accordance with the present invention. The desired end result are clear containers with sufficient mechanical and barrier properties to provide adequate protection for the contained beverage or food product. Conveniently, a container preform is formed by injection molding the polyester into a preform having a blown geometrical shape. The preform or blowable form is then contained within a mold cavity having the volumetric configuration of the desired container and the preform is expanded by blowing it with compressed air within the confines of the mold cavity. Commercially available equipment, as used in the manufacture of a single thin wall using PET beverage containers, can be used to create the containers according to embodiments of the present invention. In addition, commercial equipment such as that used in refillable wall-mounted PET containers with conventional manufacturing thickness can also be used. In accordance with the embodiments of this invention, suitable containers can be blow molded from a cylindrical injection molded preform having an open top end and neck finish. The preform may have a tapered shoulder formation portion, the substantially uniform thickness along the sides of the cylinder, and a base forming portion preferably in a champagne design, including a hemispherical base with a base cup or a base Seated design such as a petaloid design. In preferred modalities, the preform is amorphous and substantially transparent and is injection molded. According to preferred embodiments of this invention, the container preforms are subsequently placed in a blow molding apparatus having an upper mold section that engages the neck finish, and a lower mold section having a top surface which forms the concave dome portion out from the base of the container. According to a normal reheat stretch blow mold processes, the injection molded preform is first reheated to a suitable temperature for stretching and orientation of approximately 70 to 30 ° C, placed in the blow mold and a stretching rod. The axial part is then inserted into the open upper end and moved down to axially stretch the preform. Subsequently or simultaneously, an expansion gas is introduced into the interior of the preform to radially expand the shoulder, side wall and base forming portions outwardly in contact with the interior surfaces of mold sections. The resulting blow container has the same neck finish with end threads and lower neck flange as the preform. The rest of the bottle suffers from expansion although to varying degrees. A removable lid is connected to the open upper end of the container. The cap includes a base portion having internal threads that engage the external threads of the neck finish. An important consideration for producing clear or transparent containers is to produce clear or transparent preforms first. During the injection molding step, thermally induced crystallization may occur during the conversion of the polymer to a preform. The thermally induced crystallization can result in the formation of large crystallites in the polymer together with a concomitant formation of mist. In order to reduce the formation of crystallites and thus provide clear preform, the thermal crystallization regime must be slow enough so that preforms with few or no crystallites can be produced. However, the thermal crystallization regime is very slow, the production regimes of the PET resin can be adversely affected, since PET must be thermally crystallized before polymerization in the solid state, a process used to increase the molecular weight of PET and simultaneously remove the unwanted acetaldehyde. The polymerization in the solid state increases the molecular weight of the polymer, so that a container made of the polymer will have the required strength. The above techniques for reducing the rate of thermal crystallization include the use of PET containing a certain amount of co-monomers. The most commonly used comonomer modifiers are isophthalic acid or 1,4-cyclohexanedimethanol, which are added at levels ranging from 1.5 to 3.0 mole percent. To counteract the need to reduce the rate of thermal crystallization during injection molding is the need to increase the stress-induced crystallinity regime that occurs during blow molding. Stress-induced crystallization results from rapid mechanical deformation of PET, and generates extremely small transparent crystallites. The amount of crystallites present in the side wall of the container is generally correlated with the resistance and barrier performance of the container. Previously, it has been shown that the increase in SDR content of PET from 2.9 to 4.0 molar percent results in an increase in PET crystallization regimes compared to conventional PET containing between 2.4 to 2.9 mole percent of SDR. The rationale for this phenomenon is that the increased polymer chain flexibility resulting from the higher DEG content allows the polymer chains to be sorted and packaged faster in polymer crystals. In the PET copolymer of the present invention, a reduced crystallization regime ends and an increased regime of stress-induced crystallization is found to occur unexpectedly by the modification of the comonomer in NDC and DEG at lower amounts. It is thought that NDC reduces the rate of thermal crystallization due to the chain flexibility stiffness of the polymer that conceals the NDC portion, and thus makes the formation of crystallites more difficult. The addition of NDC has also been found to be less than the stiffness of the PET chains and results in an unexpected increase in the sidewall rigidity of the containers made of PET copolymer. In addition and contrary to what is expected, producing the DEG content in the PET copolymer results in an increase in the rate of stress-induced crystallization relative to conventional PET. A consequence of this unique combination of low amounts of DEG and NDC, at least in preferred embodiments there is a reduction in the natural stretch ratio of PET Copolymer compared to Conventional PET although when the VI of the PET copolymer is decreased. Normally, a lower VI PET preform could mean that the preform could have a higher stretch ratio to form a container with suitable mechanical properties. The preform of the present invention, however, defines the convention and produces a container with desirable mechanical properties although it has lower VI and a lower stretch ratio. Because this unique combination of aspects, the preform of this invention can be used to create containers in a shorter cycle time than a higher VI PET preform. Turning now to FIG. 1, a polyester preform 10 having a conventional configuration is illustrated but not drawn to scale. The preform 10 is made by injection molding of the PET copolymer of this invention and comprises a threaded neck 12 terminating at its lower end in a crown flange 14. Below the crown flange 14, there is generally a cylindrical section 16 which it ends in a section 18 of the gradually increasing end diameter so as to provide a growing wall thickness. Below section 18 there is an enlarged body section 20. The height of the preform was measured from the crown flange 14 to a closed end 21 of the enlarged body section 20. The preform 10 illustrated in Fig. 1 is molded by blown to form a container 22 illustrated in FIG. 2. The container 22 comprises a shell 24 comprising a threaded neck finish 26 defining a mouth 28, a crowning flange 30 below the threaded neck finish, a tapered section 32 extending from the crowning flange, a section of body 34 extending below the tapered section, and a base 36 at the bottom of the container. The height of the container is measured from the cap 30 to a closed end at the base 36. The container 22 is suitably used to form a packaged beverage 38, as illustrated in Fig. 2. The packaged beverage 38 includes a beverage such as carbonated soft drink disposed in the container 22 and a box 40 sealing the mouth of the container. According to the preferred embodiments of this invention, the intermediate body forming portion of the preforms of the invention can have a wall thickness of about 1.5 to about 8 mm. Further, according to preferred embodiments, the forming portion of the intermediate body of the preform can also have an internal diameter of about 10 to about 30 mm, and the height of the preform, which extends from the closed end to the opposite preform When finished, towards the finish, it is 50 to 150 mm. In one aspect, containers made in accordance with some aspects of this invention may have a volume within the range of about 0.25 to about 3 liters and a wall thickness of about 0.25 to about 0.65 mm. In this specification, reference is made to the dimensions of the preform 10 and the resulting container 22. The height H of the preforms is the distance from the closed end 21 of the preform opposite the finish 12 to the crown flange 14 of the finish. The internal diameter DI of the preforms 10 is the distance between the inner walls of the elongated body section 20 of the preforms. The wall thickness T of the preforms 10 and 11 was measured in the section of the elongate body 20 of the preforms. The wall thickness T of the preforms 10 and 11 measured in the elongated body section 20 is also of the preforms. The height H 'of the container 22 is the distance from the closed end of the base 36 of the container opposite the finish 26 to the crowning flange 30 of the finish. The maximum internal container diameter CM is the diameter of the container at its widest point along the height of the container 22. The ring stretch ratio of the preforms is equal to the maximum internal container diameter divided by the preform diameter internal and the axial stretch ratio is equal to the height of the container under the finish divided by the height of the preform under the finish. The overall stretch ratio of the preforms is equal to the product of the ring stretch ratio and the axial stretch ratio. The preform 10, container 22, and packaged beverage 38 are illustrative embodiments of the present invention. It should be understood that the GC PET copolymer comprising an aspect of the present invention can be used to create a variety of preforms and containers having a variety of configurations. The present invention was described above and is further illustrated below by way of examples, which should not be construed in any way by imposing limitations on the scope of the invention. On the contrary, it should be clearly understood that one can resort to several other modalities, molds, fiction and equivalents thereof which, after reading the present description, can be suggested to those skilled in the art without departing from the spirit of the present invention and / or scope of the appended claims.

EXAMPLE 1 The preforms were created with three different PET copolymer resins. A comparative resin Cl, was a conventional PET copolymer resin and Rl and R2 are resins made according to embodiments of this invention. Different PET resins were dried overnight at 135 ° C in a vacuum oven to achieve a moisture level below 50 ppm before injection molding. The injection molding was carried out with a laboratory scale Arburg unit cavity injection machine in conventional preform molds with a stretch ratio of approximately 14. ' The preforms were then blown free of bubbles to determine the stretch ratio of each polymer. Free blowing was carried out in each variable of the preform and bubbles were blown at temperatures of 100 ° C to 6.3 kg / cm2. The stretch ratio of each bubble was measured and recorded. A detailed description of the sample materials are listed in Table 1. A detailed description of the sample materials is listed in Table 1.

Table 1 Resin Description Table 2 Calculated air stretch ratio of free blowing bubble Table 1 shows that R1 and R2 have the same resin composition, but R2 has VI less than R1. Table 2 shows that R2 and Rl have similar natural stretch ratios. R2 has a stretch ratio less than Rl. At a VI of 0.76, R2 has a stretch ratio lower than Cl. Therefore, a preform made with R2 resin and with a configuration designed for Cl could have no problem in blow molding in a CSD container.

EXAMPLE 2 To further illustrate the stretch ratio of the embodiments of this invention having lower VI, most of the resins were made as shown in Table 3. The preforms were molded as in Example 1 and blow-free. The Cl and C2 resins where the conventional PET copolymer resin and R3 resin were also blow molded in 500 ml Coca-Cola contour bottles with an SBO 1 Sidel machine.

Table 3 Resin description Table 4 Estimated air stretch ratio of free blowing bubble Table 4 shows that when a PET of normal CSD grade is used, a low VI - (0.74) does not have a slightly higher stretch ratio than the higher VI resin (0.78). But when resins made in accordance with embodiments of the composition of the present invention are used, a low VI (0.73) still has a lower stretch ratio than the conventional upper VI PET (0.78). To further demonstrate the effect of VI, the preforms of C2 and R3 were blown in bottles as described above. This is contrary to the relationship between VI and stretch ratio for conventional PET copolymer resins. To demonstrate the effect of VI, the preforms of Cl and R3 were blown into bottles as described above using the preform configuration designed for the conventional PET copolymer Cl resin. The crystallinity of the side stop was measured in two groups of bottles using the density column method according to ASTM D 1505-85, the results are shown in Table 5.

Table 5. Crystallinity of the bottles As shown, the bottle made with C2 resin has lower criatalinity than a bottle made with R3 resin, an indication that the C2 preform of comparative resin did not stretch completely and at a higher level of orientation and crystallinity was not achieved using the preform configuration designed for conventional high VI C2 resin. To further demonstrate this, additional testing was performed on these bottles as shown below. The thermal stability test was performed according to the normal procedure of the Coca-Cola Company as described above. The thermal stability test was used to measure physical changes in bottle dimensions caused by temperature and pressure stresses. The thermal stability measurements were made in the following way: The dimensions and thickness of the test container "as received" were measured. The containers were filled with carbonated water at 4.1 +/- 0.1 volumes and crowned. The filled containers were exposed to room temperature overnight and dimensions were measured to determine percentage change. The containers were exposed to 38 ° C and the dimensions were measured to determine percent change. Twelve test samples were marked with the test and sample application numbers in the lower half of the container using a permanent ink marker. After dimensional measurements were taken at room temperature, the samples were stored in the environmental chamber at 38 ° C for 24 hours. Fill-point droplet, dome-forming and dimension measurements were completed for full containers then conditioned in the environmental chamber at 38 ° C. The minimum, maximum, average, and normal deviation values of all dimensions were calculated for each test day. The critical dimension change is listed in Table 7.

Table 6. Thermal stability of bottles As shown in Table 6, bottles made with comparative C2 resin have worse thermal expansion than those made with resin R3, indicating that the preform designed for comparative resin Cl is not suitable for the C2 resin of lower VI. However, resin R3 can use the preform design for the Cl resin of comparative top VI. In this case, the bottles made of the R3 resin meet the thermal stability specifications of the Coca-Cola Company, while the bottles made of the C2 resin do not meet the thermal stability specifications. The sidewall deflection test was performed on bottles made with resins C2 and R3 according to a modified ASTM method described below. The deflection of the side wall correlates with the stiffness of the side wall. While the force required to achieve a specific lateral wall deflection is greater, the rigidity of the bottle side wall is greater.

Table 7. Deflection of the side wall of bottles Table 7 shows that bottles made with VI resin R3 have superior side wall stiffness than that formed with conventional low C2 IV resin, an indication that resin R3 creates bottles with superior mechanical strength than bottles made with low VI C2 resin, probably due to the fact that the C2 resin is not stretched sufficiently than the upper VI Cl resin preform design to achieve high orientation and crystallinity. The bottles of Example 4 were subjected to the accelerated stress cracking test as described below. For the accelerated stress cracking resistance test, twenty-five (25) samples of each variable were randomly selected and carbonated to 4.1-4.5 volumes of C02. Samples were stored for 24 hours at 22.2 ° C and 50 RH. The base area of each bottle was immersed in a solution of dilute sodium hydroxide (0.1%.) Each bottle was carefully examined after the course of 3 hours in order to detect leakage of carbon dioxide through cracks in the base. or for catastrophic base failure If carbonation leakage or base rupture is detected, the time of this point of failure is recorded Table 8: Accelerated stress cracking As seen in Table 8, bottles made with C2 resin have very poor stress cracking resistance, while bottles made with resin R3 have acceptable stress cracking resistance. The data showed that C2 resin, as expected with low VI, can not be used to pack CSD due to the lack of stress cracking resistance. Resin R3, however, unexpectedly showed resistance to higher stress cracking.

EXAMPLE 3 To further demonstrate the benefit of the resins used according to the embodiments of this invention, a scale of low VI resins (R4, R5, and R6) were made with different compositions as shown in Table 9. The resins they were injection molded into a 500 ml preform and blown free as described in Example 1. The volume is easier to measure and does not need to be calculated compared to the air stretch ratio.

Table 9 Resin description Table 10. Free blowing results Table 10 shows that low VI resins (less than 0.75) R4, R5, and R6 made in accordance with the embodiments of this invention still have lower draw ratio than the control resin at upper VI (0.78). To further demonstrate the value of resins R4, R5, and R6, they were molded into preforms again as described in Example 1 above and blown into 500 ml contour bottles. The resins of Example 3 were injection molded into preforms and blown into bottles as in Example 1. These bottles were subjected to thermal stability measurements as in Example 2. The results are shown in Table 11.

Table 11. Thermal stability results As can be seen in Table 11, although the VI preform for resins R4 to R6 varies from 0.72 to 0.74, they behave equally in thermal stability as the comparative resin Cl with an IV preform of 0.78. It should be understood that the foregoing refers to particular embodiments of the present invention and that numerous changes can be made without departing from the scope of the invention as defined by the following claims.

Claims (38)

1. CLAIMS 1. - A preform having an open end mouth forming portion, an intermediate body forming portion and a closed base forming portion and comprising a PET copolymer comprising a diol component having repeated units of ethylene glycol and diethylene glycol and a diacid component having repeating units of terephthalic acid and naphthalenedicarboxylic acid, wherein, based on 2100 mole percent of the diol component and 100 mole percent of the diacid component, respectively, the total amount of diethylene glycol and naphthalenedicarboxylic acid present in the PET copolymer is in an amount of about 0.1 mole percent to about 2.8 mole percent and the preform has an intrinsic viscosity of less than 0.77 dL / g and a stretch ratio on the scale of about 8 to about 13 2. A preform according to claim 1, wherein the total amount of diethylene glycol ol and naphthalenedicarboxylic acid present in the PET copolymer in an amount of about 1.2 mole percent to about 2.3 mole percent. 3. A preform according to claim 1, wherein the repeated units of the naphthalenedicarboxylic acid are present in the PET copolymer in an amount from about 0.2 to about 1.0 mole percent. 4. A preform according to claim 1, wherein the repeated units of the naphthalenedicarboxylic acid are present in the PET copolymer in an amount from about 0.2 to about 0.75 mole percent. 5. A preform according to claim 1, wherein the repeated units of the naphthalenedicarboxylic acid are present in the PET copolymer in an amount from about 0.2 to about 0.75 mole percent. 6. A preform according to claim 1, wherein the repeating units of ethylene glycol are present in the PET copolymer in an amount of about 1.3 to about 2.5 mole percent. 7. A preform according to claim 1, wherein the repeating units of ethylene glycol are present in the PET copolymer in an amount of about 1.5 to about 2.2 mole percent. 8.- A preform according to the claim 1, wherein the repeated units of naphthalenedicarboxylic acid are present in the PET copolymer in an amount of from about 0.2 to about 1.0 mole percent and the repeating units of diethylene glycol are present in the PET copolymer in an amount of 1.3 to around 2.5 molar percent. 9. A preform according to claim 1, wherein the naphthalenedicarboxylic acid is a 2,6-naphthalenedicarboxylic acid. 10. A preform according to claim 1, wherein the repeated units of the naphthalenedicarboxylic acid are 2,6-naphthalenedicarboxylic acid and are present in the PET copolymer in an amount of from about 0.2 to about 1.0 mole percent and in where the repeating units of diethylene glycol are present in the PET copolymer in an amount of about 1.3 to about 2.5 mole percent. 11.- A preform according to the claim 1, wherein the preform has an intrinsic viscosity within a scale of approximately 0.60 dL / g less than 0.77 dL / g. 12. A preform according to claim 1, wherein the preform has an intrinsic viscosity less than 0.76. 13. A preform according to claim 1, wherein the preform has an intrinsic viscosity within a range of about 0.870 dL / g to less than 0.76 dL / g. 14. - A preform according to claim 1, wherein the preform has an intrinsic viscosity within a scale of about 0.70 dL / g to about 0.74 dL / g. 15.- A preform according to the claim 1, wherein the preform has a stretch ratio in the range from about 8 to about 12. 16. A container made by blow molding the preform of claim 1. 17. A container according to claim 1. 16, wherein the intermediate body forming the portion of the preform has a wall thickness of about 1.5 to about 8 mm and an internal diameter of about 10 to about 30 mm, and the preform has a finish, a closed end opposite to the finish and a closed end height to the finish of approximately 50 to about 150 mm. 18. A container according to claim 16, wherein the container has a volume within the range of about 0.25 to about 3 liters. 19. A container according to claim 16, wherein the container is a bottle, drum, chest or refrigerator. 20. - A packaged beverage comprising a container made by blow molding of the form of claim 1, and a beverage disposed in the container. 21. A method for forming a preform for use in forming containers comprising injection molding a PET copolymer comprising a diol component having repeating units of ethylene glycol and diethylene glycol, and a diacid component having repeated units of acid terephthalic acid and naphthalenedicarboxylic acid, wherein, based on 100 mole percent of the diol component and 100 mole percent of the diacid component, respectively, the total amount of diethylene glycol and naphthalenedicarboxylic acid present in the PET copolymer is an amount from about 0.1 mole percent to about 2.8 mole percent, and the preform has an intrinsic viscosity of less than 0.77 dL / g yuan ratio of stretch on the scale from about 8 to about 13. 22. A method according to claim 21, wherein the preform has an intrinsic viscosity within a scale of about 0.60 dL / g less than 0.77 dL / g. 23. A method of claim 21, wherein the preform has an intrinsic viscosity less than 0.76. 24. A method according to claim 21, wherein the preform has an intrinsic viscosity within a scale of about 0.70 dL / g to less than 0.76 dL / g. 25. A method according to claim 21, wherein the preform has an intrinsic viscosity within a range of about 0.70 dL / g to less than 0.74 dL / g. 26. A method according to claim 21, wherein the preform has a stretch ratio in the range of about 8 to about 12. 27.- A method for creating a container comprising mole blowing a molded preform by injection (a) having an open end mouth forming portion, an intermediate body forming portion and a closed base forming portion, and (b) comprising a PET copolymer comprising a diol component having repeating units of ethylene glycol and diethylene glycol and a diacid component having repeating units of terephthalic acid and naphthalenedicarboxylic acid, wherein, with 100% mole of the diol component and 100 mole percent of the diacid component, respectively, the amount total of diethylene glycol and naphthalenedicarboxylic acid present in the PET copolymer is in an amount of about 0.1 molar percent to about 2.8 percent mole, and the preform has an intrinsic viscosity of less than 0.77 dL / g and a stretch ratio in the scale of 8 to about 13. 28.- A method according to claim 27, wherein the preform it has an intrinsic viscosity within a scale of about 0.60 dL / g less than 0.77 dL / g. 29. A method according to claim 27, wherein the preform has an intrinsic viscosity less than 0.76. 30. A method according to claim 27, wherein the preform has an intrinsic viscosity within a scale of about 0.70 dL / g to less than 0.76 dL / g. 31.- A preform according to the claim 27, wherein the preform has an intrinsic viscosity within a scale of about 0.70 dL / g to less than 0.74 dL / g. 32. A method according to claim 27, wherein the preform has a stretch ratio in the range of about 8 to about 12. 33.- A method for reducing the cycle time to create a container comprising the steps of: (1) providing a copolymer melt of PET comprising a diol component having repeating units of ethylene glycol and diethylene glycol and a diacid component having repeated units of terephthalic acid and naphthalenedicarboxylic acid, wherein, based on 100 mole percent of the diol component and 100 mole percent of the diacid component, respectively, the total amount of diethylene glycol and naphthalenedicarboxylic acid present in the PET copolymer is an amount from about 0.1 mole percent to less than about 2.8 mole percent, (2) then injecting the PET copolymer into a mold, (3) then cooling the mold and the contained polymer, (4) then releasing from the mold a preform that has an intrinsic viscosity dry less than 0.77 dL / g. (5) then reheating the preform, and (6) then blow-molding the preform into a container; wherein the cycle time to create the container is reduced compared to a second cycle time to create a second container with a preform comprising a PET copolymer and having an intrinsic viscosity of at least 0.77 dL / g. 34. - A method of claim 33, wherein the preform has an intrinsic viscosity less than 0.76. 35. A method according to claim 27, wherein the preform has an intrinsic viscosity within a range of about 0.60 dL / g to less than 0.77 dL / g. 36. A method according to claim 33, wherein the preform has an intrinsic viscosity less than 0.76. 37.- A preform according to the claim 33, wherein the preform has an intrinsic viscosity within a scale of about 0.70 dL / g to less than 0.74 dL / g. 38.- A method according to claim 33, wherein the preform has a stretch ratio in the range from about 8 to about 12.